Behavioural problems in children such as delinquency, inattention, aggression and antisocial behaviour may be caused by lead poisoning.
Researchers have discovered that behaviour patterns worsened the older the child becomes, and the higher the level of lead found in his bones.
They tracked 301 boys from primary schools for four years and compared their behaviour as assessed by teachers, parents and in interviews with the level of lead found in their leg bones.
When the boys were aged seven, associations between lead levels in their bodies and their behaviour were borderline, say researchers from the University of Pittsburgh. But four years later, when the boys were 11, there were clear associations with lead and antisocial behaviour and delinquency.